1. Field of the Invention
The present invention relates to an information processing apparatus and method, and a program therefor. In particular, the present invention relates to an information processing apparatus and method, and a program therefor which are suitable for use when transferring information.
2. Description of the Related Art
A data processing apparatus to which a memory card containing a memory or the like is to be connected is known (see, Japanese Patent Laid-open No. 2004-46891, for example).
A direct memory access (DMA) controller is known that is used for data transfer between a host and storage. Direct memory access refers to transferring data directly between different memories or between a memory and an I/O device, without depending on a collection of machine language instructions. The DMA controller is a controller for controlling a DMA function.
When data is transferred using the DMA function, a descriptor is used. Data transfer control information, such as a data transfer address and a data transfer size, is described in the descriptor.
A transfer method that involves the use of the descriptor is, for example, suitably used for data transfer in the case of a discrete physical address space managed on a page-by-page basis as in a memory system used in a personal computer or the like, i.e., in the case where pieces of information that are defined as being stored in a continuous logical address space are stored discretely in an actual physical address space (see FIG. 1).